1. Field of the Invention
The present invention relates to a piezoelectric actuator, and more particularly to an actuator that is incorporated into an electronic device such as a camera or an information recording device, and serves as a drive source that precisely moves a driven unit such as a lens, and an electronic device using the actuator.
2. Description of the Related Art
In recent years, improvements in function and performance of the electronic device have been advanced, and diverse principles are applied to the actuators used in the electronic devices. In particular, a piezoelectric actuator using the piezoelectric element can be precisely positioned, is superior in responsiveness, and can be directly driven. Therefore, an attempt is made to apply the piezoelectric actuator to the positioning of the lens or a pickup in the information recording device. In particular, the piezoelectric actuator of a bimorph type having a structure in which two piezoelectric elements are bonded together and generating a bend displacement is widely used because the displacement is larger than that of the piezoelectric actuators of other types. However, in order to address a need for larger displacement output, the length of a piezoelectric element must be lengthened, and the thickness of the piezoelectric element must be thinned. As a result, the piezoelectric actuator is not practical in view of the size, rigidity, and strength.
Under the circumstances, there has been known a structure in which a plurality of bimorph elements are stacked on each other in a thickness direction (direction of the bend displacement), and one ends of the respective bimorph elements are bonded together to obtain a large displacement. A structure has been proposed in which two or even number of units each having a pair of bimorph elements that cross each other in an X-shaped configuration are stacked on each other, and fixed to each other.
However, the actuator disclosed in JP 2006-121769 A has a portion where the bimorph elements cross each other in the X-shaped configuration, and therefore the structure is complicated, the assembling is difficult, and a gap must be defined between the bimorph elements that cross each other to provide the X-shaped configuration. This leads to an increase in the size of the actuator. Further, with the above configuration, the rigidity of the actuator is reduced, and a responsiveness and the positioning controllability are deteriorated. At the same time, there arises such a problem that the actuator is liable to be affected by a posture difference to be used or a disturbance such as vibrations from outside.